Numerous scientific studies have shown that the depletion of the world's coral reefs is occurring at an alarmingly fast rate. Coral bleaching, as well as man's activities on both the land and water, have led to a decline of as much as 75-90% of the coral reefs in the waters off certain areas in the State of Florida and some estimates indicate that as much as 30% of the entire world's coral reefs have been destroyed in recent years. In addition to providing a habitat for soft and hard corals, coral reefs provide protection from coastal and beach erosion and act as a “nursery” or estuary where a variety of fish and other marine life spawn, grow and live. The coral reefs are at the bottom of the world's food chain, and are thus critical to sustaining life on the planet.
Realizing the importance of maintaining and replenishing the planet's already damaged and destroyed coral reefs, many countries have been working to reverse this trend. In the United States, governmental agencies at both the state and federal level have established artificial reef programs to study and provide solutions to the problem of disappearing reefs. A number of designs have been proposed, but most suffer from one or more deficiencies including high cost, manufacturing difficulties, poor choice of materials. and instability in moderate to severe weather and current conditions.
For example, one popular method of creating artificial reefs has been the sinking of old vessels at selected locations on the floor of an ocean or other body of water. It has been found that a number of corals do not grow well on metal, and many species of fish will not reproduce near or inside of hollow metal structures due to their tendency to resonate ambient sound or amplify noise.
Another method of encouraging the growth of coral which has been utilized in the past is the sinking of vehicle tires, either individually or bundled by attaching them together with rope or metal bands. It has been found that during periods of strong tidal or current activity, particularly during storms and hurricanes, the tires in bundles become detached from one another. These detached tires, and any individual tires placed on the ocean floor, can be moved by the tide and current into contact with existing reefs thus killing the coral and other marine life they were intended to foster.
A number of designs for artificial reefs and sea walls have been suggested in the prior art as an alternative to sunken vessels, tires and other substrates. It is recognized that artificial reefs must include multiple surfaces for coral and other sea life to attach and grow, while providing limited resistance to the flow of water from tides and current. Artificial reefs must also allow sunlight to bathe areas where the coral attaches. Structures having a number of walls interconnected to form an interior wherein each wall is formed with one or more holes or openings which intersect the interior are disclosed, for example, in U.S. Pat. Nos. 3,548,600 to Stolk, Jr. et al, U.S. Pat. No. 5,024,796 to Iwasa, U.S. Pat. No. 5,080,526 to Waters, U.S. Pat. No. 3,386,250 to Katayama, U.S. Pat. No. 5,178,006 to Lowe, U.S. Pat. No. 4,711,598 to Shaaf et al., and U.S. Pat. No. 6,186,702 to Bartkowski. The openings in the walls of structures of this type allow the flow of water through their interiors which helps stabilize them on the floor of the body of water and allows fish and other marine life to swim through their interiors. Many of these patents disclose structures having tapered or angled side walls, which, in combination with the openings in the wall(s), are intended to create an upward flow of water moving past the units. See, for example, the Shaaf et al. patent. This upward flow of water contacts and helps dissipate the force of incoming waves before they reach a beach or other coastal area, thus reducing erosion.
In addition to the stability created by openings in the walls of the units described above, it is known in the prior art to form barriers or sea walls with a bottom wall or base having one or more legs extending downwardly to contact the ocean floor. See, for example, U.S. Pat. Nos. 4,978,247 to Lenson, U.S. Pat. No. 4,089,190 to Pey and Schaaf et al. Lips or other protrusions which extend from the base of prior art patents directed to coral reefs or sea walls are shown in U.S. Pat. Nos. 3,176,468 to Nagai et al and U.S. Pat. No. 3,368,357 to Takamori. All of these designs are intended to help resist movement of the units once they are positioned on the ocean floor, even under high current or tidal conditions.
Artificial reefs and sea walls taught in the prior art can be placed on the floor of an ocean, bay or other body of water either individually or in groups. The patents to Nagai et al and Pey, for example, disclose structures in which barrier units are arranged side-by-side and/or one on top of another. The height and length of the resulting structure can be varied, as desired.
Despite efforts in the prior art to avoid some of the problems encountered with the use of sunken vessels, tires or other objects as coral reefs and sea walls, many deficiencies remain. Many artificial reefs and sea walls are constructed of concrete reinforced with steel bars. Steel bars exposed to salt water over an extended period are subject to rusting, and this has a negative effect on the growth of delicate corals and other sea life.
Although one or more artificial reef and sea wall structures taught in the prior art include hollow interiors and tapered walls with one or more openings to promote growth of coral and other marine life, as well as protrusions extending from the bottom wall to enhance stability on the floor of the ocean or other body of water, such designs are lacking in several respects. None provide an effective construction for arranging a number of individual units in a combined structure which permits the passage of marine life and water throughout the structure. In locations where the floor of the body of water is sandy or covered with silt, protrusions extending from the bottom of one or more units tend to sink in, often to different depths, causing the units to be angled relative to one another if an attempt is made to orient multiple units side-by-side or end-to-end. Rocky ocean floor areas also present a problem of alignment of adjacent units.
Even when units of the type disclosed in the prior art are used individually to create an artificial reef or sea wall, the problem of choice of materials noted above is present and many are relatively unstable when exposed to moderate to high current or tidal forces. In many designs, the weight distribution, is unacceptable compared to the overall height of the unit and they tend to topple over even if provided with protrusions or other anchoring structure on the bottom wall. Although many units include openings in one or more walls as noted above, the small size of such openings relative to the surface area of the wall in which they are formed leads to instability of the unit when impacted by tide and current forces. Such small openings also prevent larger fish from entering the units to use them for shelter, as a spawning ground or an estuarial habitat. Still other designs employ one or more openings in the side or top of the unit, but no ingress or egress for animals thus effectively trapping crustaceans and other marine life in the interior of the unit.